1. Field of the Invention
The present invention, in general relates to electrical connectors and, more particularly, to a type of electrical connector that utilizes a type MC-HL class of cable.
The MC-HL designation refers to metal clad hazardous location. MC-HL cable is typically round and includes a plurality of conductors. The MC-HL standard is defined under two Underwriters Laboratory, hereinafter referred to as “UL” specifications. The first includes UL 1569 and is entitled “Metal-Clad Cables” and the second is UL 2225 and is entitled “Metal Clad Cables and Cable-Sealing Fittings for Use in Hazardous (Classified) Locations”. The instant invention is applicable for use with all situations that fall under these two UL standards.
The preferred embodiment includes three conductors (and a ground path) that are able to carry 160 amperes at five kilovolts potential for use in hazardous locations. One such common location is to supply electrical power to an oil field wellhead. A submersible pump is commonly disposed within such an oil well. These types of cables include an armor clad exterior surrounded, typically, by a protective jacket coating.
Prior art use of an MC-HL cable includes a factory cut length of the cable that includes a desired radius and is terminated (at the factory) with the necessary connector for an electrical connection to the wellhead. Due to many heretofore unresolved issues and problems, there has been no way to cut a length of MC-HL cable in the field and attach it satisfactorily to an electrical connector that meets necessary specifications for use in hazardous locations.
Yet there remains a great need for such a field-attachable type of connector to the cable. These cables are exceedingly large and heavy. At present, when one is needed, the length of run must be carefully measured, the cable is then ordered from a manufacturer who cuts the cable to length and then attaches the connector(s) to it and then ships the completed code compliant cable assembly to the end-user.
An error in measuring the length, for example, or a change in plans requiring a longer length can delay use of a particular oil well for an extended period of time. Similarly, if a different length is needed for any reason, for example to traverse a different distance, then a new factory prepared cable must be ordered, built, and shipped. This takes time and is especially expensive.
It is not uncommon for such a cable to include a length of up to one thousand feet. Shipping such a length of heavy cable is expensive. If an existing cable is damaged by heavy equipment, for example, it too must be replaced. During such an interval, the oil well remains inoperative, which adversely affects profitability.
The manufacturer who presently provides such a product to the end user typically manufactures the connector for use with the oil wellhead, buys the cable from a cable manufacturer, cuts the cable, adds the connector(s), and then ships the finished product to the end user. This is because typically only the connector manufacturer that manufactures an electrical connector assembly that complies with NEC specifications has the knowledge and the means necessary to the attach the electrical connector to it while maintaining compliance.
As a result, shipping expense for the cable is incurred twice, once to ship the cable to the connector manufacturer from the cable manufacturer and then again to ship the finished cable to the end user.
Clearly, if the cable could be shipped only once, from the cable manufacturer to the end user that would save considerable time and shipping expense. Additionally, if the cable could be shipped in bulk lengths directly to the end user, that would result in the cable being less expensive per foot length. Finally, if that were possible, the end user would have sufficient bulk length cable for whatever tasks or repairs were to occur. However, there has not been any satisfactory method of attaching an electrical connector to the cable by the end user that can be attached in the field, by anyone, even by factory personnel who work for the connector manufacturer that, after attachment, complies with the NEC specifications.
Accordingly, it is desirable to be able to ship to the end user the cable purchased in bulk lengths and to ship separately a vastly smaller, lighter, field-attachable, disconnectable, electrical connector from the connector manufacturer for field-attachment to the cable and thereby provide the end user with versatility and the repair capability of being able to create a functioning code compliant cable with connector(s) within a few hours, and to reap substantial cost savings as a result.
Many end users would prefer to purchase the cable in bulk rolls that are shipped where the oil wells are located, for example, and then assemble the cables on demand at the site. This could decrease down time, would decrease cost, and add versatility to meet the changing needs of the end user. However, for various reasons, this has not been possible heretofore.
These reasons relate primarily to three areas involving attaching a connector to the cable, the first being issues affecting strength and other mechanical considerations, the second being issues that relate to sealing the cable to the connector, and the third being field installation issues. All of these issues must be satisfied with a high degree of certainty.
These cables are used in hazardous locations. For example, noxious and explosive gases may exist in and around the oil well. These gases, preferably, are prevented from entering into the cable and, if they do enter, they must be prevented from escaping at other than at controlled locations, where a proper vent area or vent box is provided. These gases may be under pressure, are hazardous to inhale, even deadly if inhaled in sufficient concentration, and either flammable or explosive if ignited.
It is clear then that the cable must include a sealed interface with any electrical connector that it is attached to and the resultant functionality must meet the necessary electrical code requirements for explosion-proof class of cables.
Mechanical and Strength Issues. It is necessary to ensure that the electrical cable includes sufficient strain relief so that it cannot be pulled out of the connector and dislodged. It must also maintain the necessary strength to prevent dislodging a connector pin or conductor from the pin, or pulling of the cable out of the connector, yet it must ensure that the cable and its armor are not damaged during assembly. The assembled connector must be sufficiently rugged and durable. It is also an added bonus if it can be aesthetically attractive, that is, the finished product should have the look and feel of a high-quality, durable, and professionally assembled product.
Sealing Issues. The cable must be sealed to prevent the introduction of ambient moisture. It must also be sealed sufficient to prevent the leakage of hazardous gas. It must also include sufficient internal electrical characteristics to prevent creepage, a phenomenon where an electrical arc can occur within the connector itself along a substantially linear path over a dielectric.
Field-attachable issues. Assembly must be foolproof so that it is done right the first time, even by potentially unskilled and unfamiliar labor. There must be clear instructions that, if not followed, provide a clear indication of a failure. This is especially important because it would be most hazardous if a connector were improperly attached to the cable and this was not detected, thereby resulting in use of the cable and eventual failure, perhaps in a catastrophic manner. Also, all of the above mechanical and sealing issues must also be satisfied in the field. And, the finished connector must be attachable at a 90 degree angle with respect to a longitudinal length of the cable in order to secure the connector to a mating connector half disposed on top of the wellhead. The cable will be substantially disposed along a horizontal attitude during its run and yet is must interface with the vertical mating connector at the wellhead. Adapting a heavy stiff horizontal run of MC-HL cable to mate with the vertical mating connector at the wellhead is also a mechanical issue and this issue could have been equally well included in either or in both categories.
Adding to the complexity of the problem for field-attachment issues is the rigidity of the cable itself. It is extremely difficult to work with, for example, for a field technician to attempt to bend the cable without damaging it so that it includes a radius that is useful in adapting a horizontal run of the cable to eventually mate with a vertical mating connector. Furthermore, such bending adds complexity to determining the proper overall length required for the cable. These nuances are not easily calculated in the field yet they are important considerations nevertheless. Accordingly, for ease of field-attachment one must be required only to determine the linear length of the run of cable that is required and not have to bend or introduce a radius in the MC-HL cable. This would substantially alleviate this area of complexity, yet there has heretofore been no known way of attaching an electrical connector to a horizontally disposed run of the cable that can then mate with the vertical mating connector at the wellhead and also comply with NEC specifications.
Finally, because of the need to service the well and for general access reasons, the assembled cable with connector must be disconnectable from a corresponding mating connector that is attached to the wellhead.
There are other issues as well that must also be overcome for a code compliant field attachable, disconnectable, cable.
Accordingly, there exists today a need for a field-attachable, disconnectable electrical connector for use with MC-HL cable and to provide a method for field-attachment of the connector to the cable.
Clearly, such an apparatus and method would be useful and desirable.
2. Description of Prior Art
Electrical connectors, including field-attachable connectors are, in general, known. However, there are no known field-attachable connectors for use with MC-HL cable that provide the necessary performance requirements and ease of assembly as the instant invention. While the structural arrangements of the above described known types of devices, at first appearance, may have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.